Shock strut



M @1V w Dec. 26, 1939.v K. w. WARREN 2,184,327

SHOCK STRUT` I Filed DSG. 4, 1955 BY @gw/MMV A TTORNEY.

Patented Dec. 26, 1939 SHOCK STRUT Kenneth W. Warren, South Bend, Ind., assignmto Bendix Products Corporation, South Bend, Ind., a corporation of Indiana Application December 4, 1935, Serial No. 52,762

' 2o claims. (o1. 267-64) This invention relates to shock absorbers and more particularly to metering pins employed in shock absorbers of the type wherein telescopicl cylinders are employed, and the shock of. landinto the lower chamber. In view of the fact that an emulsion of liquid and air is contained in the upper cylinder of the strut a considerable quantity 'of air is passed through the orice into the ing is dissipated by forcing a liquid to ow'from lower chamber when the strut is extended. It 6 one chamber to another through a restricted `ori has been found that considerable time'is required ce. for the air to diluse through the liquid and It is desirable, when shock absorbers are emreach the upper chamber. Unless all o f the air ployed to absorb the landing shock of aircraft, is transferred to the upper chamber, the initial that the shock absorber be designed so as to movement of the telescoping action will not be 10 provide high initial resistance so that the pneuas e'ective to dissipate energy -as where solid matic tire, commonly employed with aircraft, can liquid is contained in the lower chamber. It is be fullyvdeilected, or deflected to any desired detherefore .desirable to provide means for pergree, during the early stages of the telescoping mitting the air to diffuse through the liquid and l5 action of the strut. It is also desirablethat the reach the upper chamber as quickly as possible 15 shock absorber be so designed that variation in when the shock strut is moved to the extended. the resistance set up by the shock absorber may` position. be employed to adequately dissipate the kinetic It has also been found that where high teleenergy in the most advantageous manner to prescoping velocity of the members is encountered vent damaging the aircraft or disturbing the pasthat unlessl smooth correctly proportioned pas- 20 sengers thereof. sages are provided considerable turbulence of the In one type of shock absorber it is customary liquid isset up as the liquid is spurted through 'to position two telescoping cylinders in such rethe orifice past the metering pin. This 'turbulation that when a force is exerted on the shock lence operates to cause mixing of the liquid and absorber, a liquid contained generally in a lower the air in the upper chamber to a greater degree 25 chamber is forced through a restricted orifice than is desirable. into an upper chamber. The upper chamber is It is therefore an object of this invention to generally provided with aquantity of compressed provide a shock absorber having means to perluid such as air to provide a given degree of mit the rapid diffusion of. air through the liquid resistance sufficient to support the aircraft when to the upper chamber when -the shock absorber 30 on theground and to provide a given degree of members are moved to 4the extended position. resiliency to absorb the normal shock of taxiing Another object of the invention is to provide a the aircraft when on the ground. In shockabshock absorber having a streamlined orifice besorbers the effective area of the orifice is gentween the telescoping chambers to `permit the erally controlled by means of a metering pin so movement of the liquid from one chamber to the 35 designed as to provide a different effective oriother with the least ,possible turbulence to ince area at various stages of the telescoping acsure uniformity in the resistance developed by the tion of the shock absorber means. shock absorber.

When the shock absorber is subjected to load A still further object of the invention is to the uid or liquid contained in the lower champrovide a' shock absorber having a metering pin o ber is spurted through theorice at high velocity provided with a tapered upper section to permit to dissipate the kinetic energy of landing. Conrelatively rapid ow of air from the .liquid chamsiderable turbulence is therefore created, whereber to the air chamber when theshock absorber upon the liquid mixes with the compressed air is in the fully extended position.

45. contained in the upper chamber to form an emul` Another object of the invention is to provide a sion of liquid and air in the upper chamber. As shock absorber having a pair of telescoping liquid a greater quantity of. liquid is injected into the and air chambers separated by a piston having an upper chamber, the air therein is compressed to orifice, the effective `area of which is controlled a higher degree, whereupon more energy is abby a metering pill designed to practically close sorbedand a cushioning action is effected to abthe orice when th membgrysj'fare in the extended 50 position, and means associated with the piston Yet a further object of the invention is to pro- 55 vide a shock absorber having a liquid chamber and an air chamber separated by a streamlined orifice, and provided with a metering pin designed to permit relatively free communication between the chambers when the shock absorber is in the fully 4extended position.

Another object of the invention is to provide a metering pin.' for a shock absorber, having a cut away upper section to permit relatively free communication between the chambers of the shock absorber when the shock absorber is moved to the fully extended position.

A still further object of the invention is to provide a method of dissipating energy in a shock absorber by forcing a solidliquid through a streamlined orifice.

Other objects and advantages of this invention will be apparent from the following detailed description, considered in connection with the accompanying drawing, submitted for purposes of illustration only, and notintended to denne the scope of the invention, reference being had for that purpose to the subjoined claims, Q In the drawing, wherein similar reference characters refer to similar parts throughout the several views:

Figure l is a longitudinal view partly in section of a shock absorber embodying the present invention;

Figure 2 is an enlarged view of a portionof Figure 1;

Figure 3 is a sectional view of a portion of Figure 2 illustrating a modified forn of the-invention;

FlgureiisaviewsimilartoFigureSshowing a further modiiied form;

Flgureisaviewsimilartolligureshowing a still further modified form:

Figure 6 is a view similar in some respects to Figure 5 showing a conventional type orice and a metering pin designed to permit relatively rapid flow of air from the liquid chamber to the air chamber when ,the shock absorber is in the fully extended position; and

Figure 7 is a view showing a check valve in the piston separating the chambers, designed to permit the escape of air from the liquid chamber. Referring more particularly to Figure 1 there is shown a shock absorber having inner and outer telescoping cylinders. I0 and I2 respectively. Each of the cylinders I0 and I2 is provided with a fitting or clevice .Il and -I6 respectively, designed to permit the attachment of the shock absorber to the landing gear and fuselage of an aircraft. The lower end of the' inner cylinder I0 is closed bya piston Il, having an oriilce 20 positioned in the central portion thereof. A metering pin 22 of varying cross sectional area is carv from separating by means of a threaded sleeve 70 .contacting with 'an-abutment 2n carried 'by the 428 engaging the end of the-outer cylinder I2. and

inner cylinder III. A check tube 22 is carried by the piston I8. The check` tube $2 is'provided at its upper end with a check valve (not shown) to l permit liquid to; overnow the check tube into the ried by the lower portion ofthe outer cylinder space between the check tube I2 andthe inner walls of the cylinder Il imder certain conditions of operation. A4 plurality of orices 24 are positioned in the lower portion of the check tube 22 to permit liquid to iiow from the space between. the check tube 32 and the inner cylinder Il when the shock strut is moved in the extended position. This structure prevents too rapid separation of the cylinders.

metering pin 221s formed with a curved section 38 designed to' expose a relatively large area lfor the escape of air between the 'end of the metering pin 22 andthe inner edge of the piston I8. The

upper end of the metering pin is tapered, to cooperate with the streamlined section $6 of the piston Il to permit the ilow of liquid into the check tube 22 with the minimum of turbulence.

'l'.'he operation of the structure thus far described is as follows, When the shock strut is subjected to load "the cylinder I0 is moved down-l wardly in the cylinder l2 whereupon the inner edge of the piston I8 moves over the Aenlarged upper end of the metering pin 22, whereupon the orince 2li is practically closed. The teiescoping action of thecylinders I0 and I2 is then materially restricted and the pneumatic tire carried by the'aircraft is deflected to a desired extent. whereupona suillcient pressure is exerted upon the liquid contained in the cylinder I2 to force the cylinders to telescope. A relatively rapid rate of liquid flow from the cylinder i2 is established as the decreasing area of the metering pin 22 is projected through the oriiice 20.

It will be observed that the metering pin 22 is designed with a section of minimum cross sectional area 39 and that the metering pin'prog'ressively increases in cross sectional area from that point. In this way the energy absorbed from the shock absorber can be, controlled effectively as more particularly pointed out in the copending application of Carl V. Johnson. Serial No. 533,735, iiled April 29, 1931.

When the shock absorber approaches the completely telescoped position, the air contained in the inner cylinder l! is compressed to a high degree to support the load to which the shock ab-- sorber is subjected. When the load is removed from the absorber. the compressed air in the cylinder I0 forces the cylinders III and I2 to separate whereupon liquid ilows through the orince 2l into the outer cylinder I2. When the cylinders approach the fully extended position the metering pinA 22 is in spaced relation with repect to the piston Il of the cylinder Il so that -aportionoftheoriiicenisexposedtopermit rapid iiow of air` from the liquid cylinder I2 to the air cylinder Il.

Itwillbe observed that the orifice llisstreamlined so that a uniform flow and therefore uniform resistance to the flow -of liquid is encountered. The reliability of the shock absorber is therefo're improved. The construction of the meteringpinandoriiiceissuchastoassurea quantity of solid liquid" forthe initial operation of the strut, the liquid not being diluted by a quantity of air trapped below the piston Il, to decrease the eiliciency of the shock absorber ac- Figure 3 illustrates an embodiment of the invention wherein the' upper end of the metering pin |22 is provided with a progressivelytapering section |40. It has been found that a metering pin and orifice designed in accordance with the disclosure of Figure 3 gives very good efiiciency, and the manufacturing cost of this structure is -less than the manufacturing cost of certain other types of metering pins.

Figure 4 illustrates an embodiment of the invention wherein a metering pin having ari-enlarged upper end 242 is provided. 'I'he end ofthe pin is designed to practically close the orifice 220 in the\pi\stJQn-2I8. A slot 244 is provided in the upper end of the pin to permit the escape of trapped air from the liquid in the lower chamber to provide solid liquid for. the initial operation of .the strut.

Figure 5 shows a construction similar in many respects to Figure 4, wherein the upper end of the metering pin 342 is at on one side 350 to provide a space between the inner edge of the piston 3|8 and the metering pin to permit the escape of air from the liquid cylinder.

Figure 6 shows a metering pin 422, the upper end of which is drilled longitudinally to form a bore 460 communicating with cross bores 462 to permit the escape of air from the liquid cylinder to the air cylinder, when the shock absorber is in the fully extended position.

is in the fully extended position.

in the fully extendedposition. In this embodiment of the invention, as the shock absorber is A subjected to load the pressure of the liquid in the Y liquid cylinder closes the check valve 510 to'prevent the escape of liquid from the liquid chamber A to the air chamber through the check valve mechanism.

While the invention has been described with particular reference to several preferred embodiments, it is not intended to confine the scope of the invention to the features illustrated and described, nor otherwise than by the terms of the following claims.

I claim: 1. A shock strut having an air chamber, a liquid chamber, a piston having a streamlined oriiice positioned therein'carried by one end of the air chamber, and a metering pin carried by the' liquid cylinder and designed tovary the eifective area of the streamlined orifice and to render the orifice relatively unrestricted when, in the fully extended position to permit the escape of air from the liquid chamber and to materially restrict the oriiice upon slight telescoping mo ement of the chambers.

. 2.'In1a shock strut a liquid cylinder, an air' cylinder designed to slide into the liquid cylin.

der upon the application of forcethereto, a piston closing the lowest end of the air cylinder, a

streamlined orice positioned in the piston, a metering-pin carried by the liquid cylinder and designed to restrict the streamlined orice 'when the air cylinder is telescoped into `the liquid cylinder, the upper end of the metering pin'being designed to leave the oriiice partially unrestricted when the cylinders are in the extended. position to permit the escape of air trapped in the liquid cylinder during the extending movement of the cylinders and to abruptly restrict the oriiice during the initial telescoping movement of the cylnder.

v3'. In a shock strut a liquid chamber, an air chamber adapted to slide into the yliquid chamber, a piston having a streamlined orifice closing the lower end of the air chamber, a check tube carried by the kpiston and projecting into the 'air chamber, a metering pin carried by the liquid cylinder and adapted to vary theeective area of the streamlined orice at various telescoping po- -sitions of the shock strut, the end ofthe metering pin being designed to permit the escape of trapped air from the liquid chamber when the cylinders are in the fully extended position and to materially restrict the flow of liquid upon slight telescoping movement of the chambers.

4. A shock strut having aliquid chamber, an air chamber, a quantity of liquid in the liquid chamber, compressed air in the airl chamber, a

iov'

piston having a streamlined orifice separating restricted after `slightvmovement from the fully extended position.

5. In a telescoping shock strut having alliquidcylinder, an air cylinder, a quantity of liquid in the liquid cylinder,4 compressed air in the air cylinder, a piston having a streamlined orifice separating the cylinders, a metering pin designed to vary the @effective area of the streamlined oriiice at various operating positions and pro-A vided With a slotted upper vend to render the orifice substantially unrestricted when the strut is in the fully'extended position and to render the orifice substantially restricted when the strut is moved slightly from the fully extended position.

6. In a telescoping shock strut having a liquid cylinder, an air cylinder, a quantity of liquid in f the liquid cylinder, compressed', air in the air cylinder, a piston having an orifice separating the cylinders, a metering pin designed to `vary the effective .area of the orifice at `various operating positions and provided with a ,longitudinal bore' communicating with cross bores in the upper end to render the orifice substantially unrestricted when the strut is in the fully extended position and substantially restrictedwhen the cross bores pass through said oriilce.

7. In a shock strut. a liquid cylinder, an air cylinder designed to slide into the liquid cylinder, packing means between the liquid 'and air cylinders, a piston having a'streamlined orifice carried-by the lower end of the air cylinder. a

` metering pin designed to varythe eiiective area of the streamlined orice atvarious operating positions, the upper end of the metering pin being tapered on one side to permit relatively free communication lbetween the cylinders when in the position. A v

8. Ashock strut having an upper chamber, a lower chamber,'a piston-,having astreamlined orifice positioned therein associated with the upper chamber, and a metering pin associated with the lower chamber and designed-to vary the effective area of the oriiice and'to render the orifice suiiiciently unrestricted when thestrut is in the fully extended position to materially restrict the v ilow of liquid.

9. A shock strut having an air chamber, a liquid chamber, a piston having an orice positionedtherein carried by one end oi the air chamber, and a metering pin carried by the liquid cylinder anddesigned to vary the eiective area of the orifice and to render the orifice relatively unrestricted when in the fully extended position to permit the escape of air from the liquid chamber and to materially restrict the orince upon slight telescoping movement of the chambers.

10. In a shock strut a liquid cylinder, an air cylinder designed to slide into .the liquid cylinder upon the application of force thereto, a piston closing the lowestvend of the air cylinder, an oriilce positioned inthe piston, a metering .pin carried by the liquid cylinder and designed to restrict the streamlined oriiice when theair cylinder is telescoped into the liquid cylinder, the

Aupper end of the metering pin being designed to leave the ermee-partially unrestricted when the cylinders are in the extended position to permit the escape of air trapped in the liquid cylinder during the extending movement o! the cylinders and to abruptly restrict the orifice during the initial telescoping movement of the cylinder.

11. In a shockstrut aliqu'd chamber, an air chamber adapted to slide into the liquid chamber, a piston having an orliice closing the lower end ofthe air chamber, a check tube carried by the piston and projecting'into the air chamber. a

metering pin carried by the liquid cylinder and y adapted to vary'the effective area of the orifice at various telescoping positions of theV shock strut, the end'of the metering pin being designed to permit the escape ofv trapped air from the liquid chamber when the cylinders are in the fully extended position and to materially restrict the ilow of liquid upon slight teleseoping movement of the chambers. Y

12.Ashockstruthavingaiiquidchamber,an.

air chamber, a quantity of liquid in the liquid chamber, compressed air in the air' chamber. a pistonhaving an orifice separating the chamb`ers. a metering Pin designed tovary the eilec# tive area of the oriilceat various operating positions and to render-the oriilce substantially unrestricted when the strut is in the fully extended position and substantially restricted vafter slight movement from the fully extended position.

13. In a. telescoping shock strut having a liquid cylinder, an air cylinder, a quantity of liquid in the liquid cylinder., compressed air in the air cylinder, a piston having an oriiiceaepara'ting and to render the orifice substantially when the strut is moved fronlthe fully extended position.

14. nr a sneek :bruta pairefreleseopmg liquid and air cylinders, packing means between the liquid and air cylinders. a piston havingan orince-carried by the -lowerendoi' one or the cyl- ,n inders, a metering pin'designed to vary. the clicctive area oi the mince' at various -posiv tions, the upper end of the metering pim being tapered on one side to permit relatively free communication between the cylinders when in the fully extended position and to materially restrict the orice in the slightly telescoped position.

15. A shock strut having an upper chamber, a

-lower chamber, a. piston having an orifice posiltioned therein associated with. the upper chamber, and a metering pin associated with the lower chamber and designed to vary the effective area o! the orifice and to render the orlilce sulciently unrestricted when the strut is in the fully extended position to permit the escape of air from the lower chamber and sufficiently restricted when the' -strut is moved slightly from the fully extended position to materially restrict the ilow of liquid.

16. In a shock strut having telescoping liquid andiluid cylinders, a quantity oi liquid in the liquid cylinder, a quantity oi compressed uid in the uid cylinder, a partial closure including an orifice between the cylinders, a check tube having a plurality of metering oriilces at the lower end carried by the partial closure, a check valve at the upper end of the check tube, and a metering pin designed to slide within thecheck tube and to vary the effective area of the orifice at various operating positions and to render the oriilce substantially unrestricted when the strut is in the fully extended position and substantially restricted after slight movement from the fully extended position.

17.. ThatA method of absorbing the landing shock of aircraft which comprises forcing a liquid from one chamber to another chamber containing a quantity of compressed fluid, and controlling 'the rate of liquid f low in such a` manner that the liquid iiow is relatively unrestricted when the landing shock is applied and the resistance tothe ilow-oi liquid is rapidly restricted after the land-r ing shock'is Aapplied and is then progressively decreased and increased as the load is applied.

18. The method'of absorbing the landing v shock of aircraft which comprises Vthe steps oi forcing a liquid from one chamber to another chamber containing aqgantity of compressed uid through a relatively unrestricted opening when the landing shock is rst applied and rapidly restricting .the opening immediately thereafter.

19. Themethod of absorbing the landing shockoi aircraft which comprises forcing liquid from one chamber to another chamber containing a quantity of compressed fluid through a.; relatively unrestricted orlilce, partially closing the orifice immediately after the landing shock has been effected. increasing the eiIective size of the orifice progressively thereafter asf-the landing load is received, and removing the restriction oi the orifice when the load is removed.

20. A shock strut having a pair of chambers, a piston having an oriiice positioned therein carrled'by one end oi one chamber, and a metering pin carried by the other chamber and designed to vary the effective area of the oriilce to render the kcince relatively unrestricted when the structure is inthe fully 'extended position te permitthe 4escape oi air from the second named chambe and to materially restrict the orince upon slightly telescoping movement of the chambers. 

